The perception of form is one of the most basic functions of the visual system. Because motion and dynamic occlusions are ubiquitous in our environment, understanding how the human visual system computes the form of moving objects in the presence of occlusions is a fundamental problem in vision science. An analysis of dynamic aspects of vision shows that non-retinotopic computational principles and mechanisms are needed to compute the form of moving objects. We designate as "non-retinotopic" those mechanisms that can generate perception of form in the absence of a retinotopic image. Indeed, perceptual data demonstrate that a retinotopic image is neither necessary nor sufficient for the perception of form. The broad long-term objective of this research is to elucidate the mechanisms underlying visual form perception under its natural dynamic conditions. In particular, we want to characterize non-retinotopic computational principles and mechanisms that allow the visual system to compute the form of moving objects. We hypothesize that a synergy between masking, perceptual grouping, and motion estimation mechanisms can provide a unified visual processing framework that can be applied to natural dynamic viewing conditions. We will address the following two specific aims. Specific Aim 1: Elucidate non-retinotopic mechanisms of dynamic form perception by using anorthoscopic perception. Anorthoscopic perception provides a clear demonstration of the existence of non- retinotopic mechanisms. Do such mechanisms also contribute to dynamic perception in the absence of occlusions? By using a stimulus paradigm, known as the Ternus-Pikler display, we have recently discovered a new illusion that shows non-retinotopic feature perception for moving objects in the absence of occlusions. We will use this paradigm to generalize non-retinotopic mechanisms to dynamic vision: Specific Aim 2: Elucidate the role of non-retinotopic mechanisms in dynamic form perception in the absence of occlusions by using variants of Ternus-Pikler displays. PUBLIC HEALTH RELEVANCE: The proposed studies are expected to improve our understanding of how the human visual system works. This understanding can be instrumental in diagnosing, treating disorders of the visual system in particular, and the nervous system in general.